Aniline, a toxic aromatic amine, is a widely used industrial chemical, particularly in the manufacture of dyes, pigments and drugs. The hemopoietic system is an early target of aniline insult. Besides causing methemoglobinemia and hemolytic anemia, aniline exposure also results in selective splenic toxicity leading to splenomegaly, hemorrhage, capsular hyperplasia, fibrosis and eventually a variety of sarcomas. Little is known about the mechanism(s) by which aniline and aniline-related compounds induce selective damage to spleen which is the focus of this project. Our preliminary subchronic studies in rats indicate time dependent deposition of iron, vascular congestion and fibro is of the spleen as a result of aniline exposure. Our data also indicates covalent binding and accumulation of radioactivity in the spleens of rats exposed to 14C-aniline HCl. My overall objective is to determine how and why aniline causes selective damage to spleen. In these studies a special emphasis will be given to assess the role of iron overload and its relationship to aniline metabolites which result in covalent binding to macromolecules. Aim 1 will elucidate the possible mechanisms of the selective effects of aniline on spleen in terms of free radical formation, lipid peroxidation, protein oxidation, covalent binding and morphological changes resulting from in vivo exposure in rats. Aim 2 will elucidate the role of iron overload in the aniline-induced splenic toxicity, by studying (i) potentiation of toxicity by increasing iron load (ii) diminution of the toxicity by reducing the iron load. Aim 3 will identify the splenotoxic metabolites (N- and ring-hydroxylated) of aniline. This will be achieved by conducting toxicity studies in rats with known metabolites of aniline. If known metabolite(s) are not found to be splenotoxic, then new metabolite(s) identified under Specific Aim 1 will be tested for toxicity. These studies will provide the mechanism(s) of aniline-induced splenotoxicity and will also define the role of iron and aniline metabolites in the observed toxicity. The information obtained from these studies can be further used to develop preventive strategies.